\r \r

CWICR Cost Calculator\r

\r

Business Case\r

\r

Problem Statement\r

Traditional cost estimation often produces "black box" estimates with hidden markups. Stakeholders need:\r

• Transparent cost breakdowns\r
• Traceable pricing logic\r
• Auditable calculations\r
• Resource-level detail\r \r

Solution\r

Resource-based cost calculation using CWICR methodology that separates physical norms (labor hours, material quantities) from volatile prices, enabling transparent and auditable estimates.\r \r

Business Value\r

• Full transparency - Every cost component visible\r
• Auditable - Traceable calculation logic\r
• Flexible - Update prices without changing norms\r
• Accurate - Based on 55,000+ validated work items\r \r

Technical Implementation\r

\r

Prerequisites\r

pip install pandas numpy\r
```\r
\r
### Python Implementation\r
\r
```python\r
import pandas as pd\r
import numpy as np\r
from typing import Dict, Any, List, Optional, Tuple\r
from dataclasses import dataclass, field\r
from enum import Enum\r
from datetime import datetime\r
\r
\r
class CostComponent(Enum):\r
    """Cost breakdown components."""\r
    LABOR = "labor"\r
    MATERIAL = "material"\r
    EQUIPMENT = "equipment"\r
    OVERHEAD = "overhead"\r
    PROFIT = "profit"\r
    TOTAL = "total"\r
\r
\r
class CostStatus(Enum):\r
    """Cost calculation status."""\r
    CALCULATED = "calculated"\r
    ESTIMATED = "estimated"\r
    MISSING_DATA = "missing_data"\r
    ERROR = "error"\r
\r
\r
@dataclass\r
class CostBreakdown:\r
    """Detailed cost breakdown for a work item."""\r
    work_item_code: str\r
    description: str\r
    unit: str\r
    quantity: float\r
\r
    labor_cost: float = 0.0\r
    material_cost: float = 0.0\r
    equipment_cost: float = 0.0\r
    overhead_cost: float = 0.0\r
    profit_cost: float = 0.0\r
\r
    unit_price: float = 0.0\r
    total_cost: float = 0.0\r
\r
    labor_hours: float = 0.0\r
    labor_rate: float = 0.0\r
\r
    resources: List[Dict[str, Any]] = field(default_factory=list)\r
    status: CostStatus = CostStatus.CALCULATED\r
\r
    def to_dict(self) -> Dict[str, Any]:\r
        return {\r
            'work_item_code': self.work_item_code,\r
            'description': self.description,\r
            'unit': self.unit,\r
            'quantity': self.quantity,\r
            'labor_cost': self.labor_cost,\r
            'material_cost': self.material_cost,\r
            'equipment_cost': self.equipment_cost,\r
            'overhead_cost': self.overhead_cost,\r
            'profit_cost': self.profit_cost,\r
            'total_cost': self.total_cost,\r
            'status': self.status.value\r
        }\r
\r
\r
@dataclass\r
class CostSummary:\r
    """Summary of cost estimate."""\r
    total_cost: float\r
    labor_total: float\r
    material_total: float\r
    equipment_total: float\r
    overhead_total: float\r
    profit_total: float\r
\r
    item_count: int\r
    currency: str\r
    calculated_at: datetime\r
\r
    breakdown_by_category: Dict[str, float] = field(default_factory=dict)\r
\r
\r
class CWICRCostCalculator:\r
    """Resource-based cost calculator using CWICR methodology."""\r
\r
    DEFAULT_OVERHEAD_RATE = 0.15  # 15% overhead\r
    DEFAULT_PROFIT_RATE = 0.10   # 10% profit\r
\r
    def __init__(self, cwicr_data: pd.DataFrame,\r
                 overhead_rate: float = None,\r
                 profit_rate: float = None,\r
                 currency: str = "USD"):\r
        """Initialize calculator with CWICR data."""\r
        self.data = cwicr_data\r
        self.overhead_rate = overhead_rate or self.DEFAULT_OVERHEAD_RATE\r
        self.profit_rate = profit_rate or self.DEFAULT_PROFIT_RATE\r
        self.currency = currency\r
\r
        # Index data for fast lookup\r
        self._index_data()\r
\r
    def _index_data(self):\r
        """Create index for fast work item lookup."""\r
        if 'work_item_code' in self.data.columns:\r
            self._code_index = self.data.set_index('work_item_code')\r
        else:\r
            self._code_index = None\r
\r
    def calculate_item_cost(self, work_item_code: str,\r
                            quantity: float,\r
                            price_overrides: Dict[str, float] = None) -> CostBreakdown:\r
        """Calculate cost for single work item."""\r
\r
        # Find work item in database\r
        if self._code_index is not None and work_item_code in self._code_index.index:\r
            item = self._code_index.loc[work_item_code]\r
        else:\r
            # Try partial match\r
            matches = self.data[\r
                self.data['work_item_code'].str.contains(work_item_code, case=False, na=False)\r
            ]\r
            if matches.empty:\r
                return CostBreakdown(\r
                    work_item_code=work_item_code,\r
                    description="NOT FOUND",\r
                    unit="",\r
                    quantity=quantity,\r
                    status=CostStatus.MISSING_DATA\r
                )\r
            item = matches.iloc[0]\r
\r
        # Get base costs\r
        labor_unit = float(item.get('labor_cost', 0) or 0)\r
        material_unit = float(item.get('material_cost', 0) or 0)\r
        equipment_unit = float(item.get('equipment_cost', 0) or 0)\r
\r
        # Apply price overrides if provided\r
        if price_overrides:\r
            if 'labor_rate' in price_overrides:\r
                labor_norm = float(item.get('labor_norm', 0) or 0)\r
                labor_unit = labor_norm * price_overrides['labor_rate']\r
            if 'material_factor' in price_overrides:\r
                material_unit *= price_overrides['material_factor']\r
            if 'equipment_factor' in price_overrides:\r
                equipment_unit *= price_overrides['equipment_factor']\r
\r
        # Calculate component costs\r
        labor_cost = labor_unit * quantity\r
        material_cost = material_unit * quantity\r
        equipment_cost = equipment_unit * quantity\r
\r
        # Direct costs\r
        direct_cost = labor_cost + material_cost + equipment_cost\r
\r
        # Overhead and profit\r
        overhead_cost = direct_cost * self.overhead_rate\r
        profit_cost = (direct_cost + overhead_cost) * self.profit_rate\r
\r
        # Total\r
        total_cost = direct_cost + overhead_cost + profit_cost\r
\r
        # Unit price\r
        unit_price = total_cost / quantity if quantity > 0 else 0\r
\r
        return CostBreakdown(\r
            work_item_code=work_item_code,\r
            description=str(item.get('description', '')),\r
            unit=str(item.get('unit', '')),\r
            quantity=quantity,\r
            labor_cost=labor_cost,\r
            material_cost=material_cost,\r
            equipment_cost=equipment_cost,\r
            overhead_cost=overhead_cost,\r
            profit_cost=profit_cost,\r
            unit_price=unit_price,\r
            total_cost=total_cost,\r
            labor_hours=float(item.get('labor_norm', 0) or 0) * quantity,\r
            labor_rate=float(item.get('labor_rate', 0) or 0),\r
            status=CostStatus.CALCULATED\r
        )\r
\r
    def calculate_estimate(self, items: List[Dict[str, Any]],\r
                          group_by_category: bool = True) -> CostSummary:\r
        """Calculate cost estimate for multiple items."""\r
\r
        breakdowns = []\r
        for item in items:\r
            code = item.get('work_item_code') or item.get('code')\r
            qty = item.get('quantity', 0)\r
            overrides = item.get('price_overrides')\r
\r
            breakdown = self.calculate_item_cost(code, qty, overrides)\r
            breakdowns.append(breakdown)\r
\r
        # Aggregate totals\r
        labor_total = sum(b.labor_cost for b in breakdowns)\r
        material_total = sum(b.material_cost for b in breakdowns)\r
        equipment_total = sum(b.equipment_cost for b in breakdowns)\r
        overhead_total = sum(b.overhead_cost for b in breakdowns)\r
        profit_total = sum(b.profit_cost for b in breakdowns)\r
        total_cost = sum(b.total_cost for b in breakdowns)\r
\r
        # Group by category if requested\r
        breakdown_by_category = {}\r
        if group_by_category:\r
            for b in breakdowns:\r
                # Extract category from work item code prefix\r
                category = b.work_item_code.split('-')[0] if '-' in b.work_item_code else 'Other'\r
                if category not in breakdown_by_category:\r
                    breakdown_by_category[category] = 0\r
                breakdown_by_category[category] += b.total_cost\r
\r
        return CostSummary(\r
            total_cost=total_cost,\r
            labor_total=labor_total,\r
            material_total=material_total,\r
            equipment_total=equipment_total,\r
            overhead_total=overhead_total,\r
            profit_total=profit_total,\r
            item_count=len(breakdowns),\r
            currency=self.currency,\r
            calculated_at=datetime.now(),\r
            breakdown_by_category=breakdown_by_category\r
        )\r
\r
    def calculate_from_qto(self, qto_df: pd.DataFrame,\r
                          code_column: str = 'work_item_code',\r
                          quantity_column: str = 'quantity') -> pd.DataFrame:\r
        """Calculate costs from Quantity Takeoff DataFrame."""\r
\r
        results = []\r
        for _, row in qto_df.iterrows():\r
            code = row[code_column]\r
            qty = row[quantity_column]\r
\r
            breakdown = self.calculate_item_cost(code, qty)\r
            result = breakdown.to_dict()\r
\r
            # Add original QTO columns\r
            for col in qto_df.columns:\r
                if col not in result:\r
                    result[f'qto_{col}'] = row[col]\r
\r
            results.append(result)\r
\r
        return pd.DataFrame(results)\r
\r
    def apply_regional_factors(self, base_costs: pd.DataFrame,\r
                               region_factors: Dict[str, float]) -> pd.DataFrame:\r
        """Apply regional adjustment factors."""\r
        adjusted = base_costs.copy()\r
\r
        if 'labor_cost' in adjusted.columns and 'labor' in region_factors:\r
            adjusted['labor_cost'] *= region_factors['labor']\r
\r
        if 'material_cost' in adjusted.columns and 'material' in region_factors:\r
            adjusted['material_cost'] *= region_factors['material']\r
\r
        if 'equipment_cost' in adjusted.columns and 'equipment' in region_factors:\r
            adjusted['equipment_cost'] *= region_factors['equipment']\r
\r
        # Recalculate totals\r
        adjusted['direct_cost'] = (\r
            adjusted.get('labor_cost', 0) +\r
            adjusted.get('material_cost', 0) +\r
            adjusted.get('equipment_cost', 0)\r
        )\r
        adjusted['total_cost'] = adjusted['direct_cost'] * (1 + self.overhead_rate) * (1 + self.profit_rate)\r
\r
        return adjusted\r
\r
    def compare_estimates(self, estimate1: CostSummary,\r
                         estimate2: CostSummary) -> Dict[str, Any]:\r
        """Compare two cost estimates."""\r
        return {\r
            'total_difference': estimate2.total_cost - estimate1.total_cost,\r
            'total_percent_change': (\r
                (estimate2.total_cost - estimate1.total_cost) /\r
                estimate1.total_cost * 100 if estimate1.total_cost > 0 else 0\r
            ),\r
            'labor_difference': estimate2.labor_total - estimate1.labor_total,\r
            'material_difference': estimate2.material_total - estimate1.material_total,\r
            'equipment_difference': estimate2.equipment_total - estimate1.equipment_total,\r
            'item_count_difference': estimate2.item_count - estimate1.item_count\r
        }\r
\r
\r
class CostReportGenerator:\r
    """Generate cost reports from calculations."""\r
\r
    def __init__(self, calculator: CWICRCostCalculator):\r
        self.calculator = calculator\r
\r
    def generate_summary_report(self, items: List[Dict[str, Any]]) -> Dict[str, Any]:\r
        """Generate summary cost report."""\r
        summary = self.calculator.calculate_estimate(items)\r
\r
        return {\r
            'report_date': datetime.now().isoformat(),\r
            'currency': summary.currency,\r
            'total_cost': round(summary.total_cost, 2),\r
            'breakdown': {\r
                'labor': round(summary.labor_total, 2),\r
                'material': round(summary.material_total, 2),\r
                'equipment': round(summary.equipment_total, 2),\r
                'overhead': round(summary.overhead_total, 2),\r
                'profit': round(summary.profit_total, 2)\r
            },\r
            'percentages': {\r
                'labor': round(summary.labor_total / summary.total_cost * 100, 1) if summary.total_cost > 0 else 0,\r
                'material': round(summary.material_total / summary.total_cost * 100, 1) if summary.total_cost > 0 else 0,\r
                'equipment': round(summary.equipment_total / summary.total_cost * 100, 1) if summary.total_cost > 0 else 0,\r
            },\r
            'item_count': summary.item_count,\r
            'by_category': summary.breakdown_by_category\r
        }\r
\r
    def generate_detailed_report(self, items: List[Dict[str, Any]]) -> pd.DataFrame:\r
        """Generate detailed line-item report."""\r
        results = []\r
\r
        for item in items:\r
            code = item.get('work_item_code') or item.get('code')\r
            qty = item.get('quantity', 0)\r
\r
            breakdown = self.calculator.calculate_item_cost(code, qty)\r
            results.append(breakdown.to_dict())\r
\r
        df = pd.DataFrame(results)\r
\r
        # Add totals row\r
        totals = df[['labor_cost', 'material_cost', 'equipment_cost',\r
                     'overhead_cost', 'profit_cost', 'total_cost']].sum()\r
        totals['description'] = 'TOTAL'\r
        totals['work_item_code'] = ''\r
\r
        df = pd.concat([df, pd.DataFrame([totals])], ignore_index=True)\r
\r
        return df\r
\r
\r
# Convenience functions\r
def calculate_cost(cwicr_data: pd.DataFrame,\r
                   work_item_code: str,\r
                   quantity: float) -> float:\r
    """Quick cost calculation."""\r
    calc = CWICRCostCalculator(cwicr_data)\r
    breakdown = calc.calculate_item_cost(work_item_code, quantity)\r
    return breakdown.total_cost\r
\r
\r
def estimate_project_cost(cwicr_data: pd.DataFrame,\r
                         items: List[Dict[str, Any]]) -> Dict[str, Any]:\r
    """Quick project cost estimate."""\r
    calc = CWICRCostCalculator(cwicr_data)\r
    report = CostReportGenerator(calc)\r
    return report.generate_summary_report(items)\r
```\r
\r
## Quick Start\r
\r
```python\r
import pandas as pd\r
from cwicr_data_loader import CWICRDataLoader\r
\r
# Load CWICR data\r
loader = CWICRDataLoader()\r
cwicr = loader.load("ddc_cwicr_en.parquet")\r
\r
# Initialize calculator\r
calc = CWICRCostCalculator(cwicr)\r
\r
# Calculate single item\r
breakdown = calc.calculate_item_cost("CONC-001", quantity=150)\r
print(f"Total: ${breakdown.total_cost:,.2f}")\r
print(f"  Labor: ${breakdown.labor_cost:,.2f}")\r
print(f"  Material: ${breakdown.material_cost:,.2f}")\r
print(f"  Equipment: ${breakdown.equipment_cost:,.2f}")\r
```\r
\r
## Common Use Cases\r
\r
### 1. Project Estimate\r
```python\r
items = [\r
    {'work_item_code': 'CONC-001', 'quantity': 150},\r
    {'work_item_code': 'EXCV-002', 'quantity': 200},\r
    {'work_item_code': 'REBAR-003', 'quantity': 15000}  # kg\r
]\r
\r
summary = calc.calculate_estimate(items)\r
print(f"Project Total: ${summary.total_cost:,.2f}")\r
```\r
\r
### 2. QTO Integration\r
```python\r
# Load BIM quantities\r
qto = pd.read_excel("quantities.xlsx")\r
\r
# Calculate costs\r
costs = calc.calculate_from_qto(qto,\r
    code_column='work_item',\r
    quantity_column='quantity'\r
)\r
print(costs[['description', 'quantity', 'total_cost']])\r
```\r
\r
### 3. Regional Adjustment\r
```python\r
# Apply Berlin pricing\r
berlin_factors = {\r
    'labor': 1.15,      # 15% higher labor\r
    'material': 0.95,   # 5% lower materials\r
    'equipment': 1.0\r
}\r
\r
adjusted = calc.apply_regional_factors(costs, berlin_factors)\r
```\r
\r
## Resources\r
\r
- **GitHub**: [OpenConstructionEstimate-DDC-CWICR](https://github.com/datadrivenconstruction/OpenConstructionEstimate-DDC-CWICR)\r
- **DDC Book**: Chapter 3.1 - Construction Cost Estimation\r